Reproduce Figure 3.2 in Introduction to Statistical Learning

Has anyone reproduced Figure 3.2 in Introduction to Statistical Learning (James et al)?

https://trevorhastie.github.io/ISLR/ISLR%20Seventh%20Printing.pdf

They have a contour plot with circles.

Here is my code, which produces a contour plot with ellipses. Some of the numbers appear close, but some others are very different.

library(tidyverse)

# dataset can be found here: https://trevorhastie.github.io/ISLR/data.html
advert <- read_csv('Advertising.csv')

calc_ssr <- function(b0, b1){
  r <- advert$sales - (b0 + b1 * advert$TV)
  sum(r^2)
}

b0_range <- seq(5, 9, length.out = 25)
b1_range <- seq(0.03, 0.065, length.out = 25)
params <- crossing(b0 = b0_range, b1 = b1_range)
params$ssr <- map2_dbl(params$b0, params$b1, calc_ssr)

params %>% 
  ggplot(aes(x = b0, y = b1, z = ssr)) + 
  geom_contour_filled(breaks = c(2100, 2150, 2200, 2300, 2500, 3000))
```